CN110003717B

CN110003717B - Steganography material and steganography method based on surface-enhanced Raman nanoparticles

Info

Publication number: CN110003717B
Application number: CN201910183338.8A
Authority: CN
Inventors: 叶坚; 顾雨清
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2019-03-12
Filing date: 2019-03-12
Publication date: 2022-03-11
Anticipated expiration: 2039-03-12
Also published as: CN110003717A

Abstract

The invention discloses a steganography material based on surface-enhanced Raman nanoparticles and a steganography method, and relates to the field of materials and the field of information security. The steganographic material based on the surface enhanced Raman nanoparticles is a mixed material with the surface enhanced Raman nanoparticles added into a common material. The surface enhanced raman nanoparticles are composed of a metallic nanomatrix and a characteristic raman molecule, the metallic nanomatrix being gold. The steganography method of the invention uses one or more steganography materials and common materials to record information respectively for encryption. And reading the Raman spectrum information of the steganographic material and the common material by utilizing a Raman spectrometer for scanning or imaging, extracting and optimizing coefficients of different components by using an algorithm to obtain an optimal fitting spectrum, finishing background noise elimination and combination selection of different steganographic materials, obtaining hidden information, and finishing decryption. The invention has the characteristics of safety, low cost, strong signal, good light stability and environment stability, and capability of carrying out information combination multiplexing.

Description

Steganography material and steganography method based on surface-enhanced Raman nanoparticles

Technical Field

The invention relates to the field of materials and information security, in particular to a steganographic material and a steganographic method based on surface-enhanced Raman nanoparticles.

Background

With the development of information technology, the problem of information security is increasingly highlighted. The information leakage not only damages privacy of individuals and enterprises, but also can seriously threaten national confidentiality and security. Therefore, the protection of important information is a very urgent need. Steganography is a commonly used information protection technique that means that information that is desired to be transferred is hidden in other information and the transfer and content of the information is not known to anyone other than the intended recipient. Steganography has the advantage over another conventional information protection technique, cryptography, that the information that is transferred is not noticed or suspected by others. Steganographic ink is a commonly used steganographic material in steganographic technology. The information written with the ink is invisible to the naked eye and can only be presented by a certain developing mode. The steganographic ink can be divided into various types according to the development mode, including thermal development ink, chemical development ink, photo development ink and the like. Compared with the former two, the optical development mode has the advantages of safety, no damage to information and realization of complex information combination. The photo-developing ink is mainly fluorescent ink, and emits fluorescence under the irradiation of laser with certain wavelength to present hidden information. However, fluorescent inks have their drawbacks. The traditional organic fluorescent dye ink is easy to photobleach and poor in light stability, and the fluorescence cross color phenomenon limits the multiplexing of information combination; the newly developed quantum dot or rare earth ink has good light stability and narrow spectrum peak, but may have toxicity to human body and environment, and has high cost.

Therefore, those skilled in the art are devoted to develop a steganographic material and a steganographic method based on surface-enhanced raman nanoparticles, which are not only safe, low in cost, strong in signal, good in light stability and environment stability, but also have the capability of multiplexing information combination.

Disclosure of Invention

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to find a steganographic material and a steganographic method that are safe, low in cost, strong in signal, good in light stability and environment stability, and capable of multiplexing information combinations.

In order to achieve the purpose, the invention provides a steganographic material based on surface-enhanced Raman nanoparticles, wherein the surface-enhanced Raman nanoparticles are added into the steganographic material.

Further, the surface-enhanced raman nanoparticles are comprised of a metallic nanomatrix and a characteristic raman molecule.

Further, the metal in the metal nanomatrix is gold.

Further, the structure of the metal nano-substrate comprises a nano core-shell particle structure, a nano flower, a nano triangular plate, a nano sphere, a nano rod, a nano star, a nano dendrite and a nano particle dimer.

Further, the characteristic Raman molecule includes p-dimercaptobenzene (1,4-BDT), 4-nitrothiophenol (4-NBT), o-nitrothiophenol (2-NBT), 2-mercapto-5-nitrobenzimidazole (2-M-5-NBI), 2-mercapto-6-nitrobenzothiazole (2-M-6-NBT), biphenyl-4, 4 '-dithiol (4,4' -BPDT), 4-toluenethiol (4-MBT), o-chlorothiophenol (2-CBT), 4-chlorothiophenol (4-CBT), and 2-napthalenethiol (2-NT).

Alternatively, the steganographic material includes, but is not limited to, a steganographic ink, a steganographic toner, a steganographic pigment, or a steganographic paint. Such as a steganographic pen ink, a steganographic writing brush ink, a steganographic printing pigment, and the like.

The invention also provides a steganography method using the steganography material based on the surface enhanced Raman nanoparticles, which comprises the following steps:

step 1, the Party A records information by using one or more of the steganographic materials based on the surface-enhanced Raman nanoparticles and common materials respectively and encrypts the information;

step 2, the party A transmits the encryption mode and the combination mode to the party B;

step 3, the party A transmits the record information to the party B;

step 4, the second party utilizes a Raman spectrometer to scan or image and read the Raman spectrum information of the one or more steganographic materials based on the surface enhanced Raman nanoparticles and the common materials;

step 5, the second party obtains the optimal fitting spectrum by optimizing coefficients of different components by using a specific algorithm on the obtained Raman spectrum information;

and 6, the second party combines the optimal fitting spectrum according to the encryption mode and the combination mode, and decrypts the optimal fitting spectrum to obtain hidden information.

Further, the common material in the step 1 and the step 4 includes common ink, common toner, common pigment, or common paint.

Further, the specific algorithm used in the step 5 comprises a classical least squares method.

Further, the scanning mode in the imaging process of the Raman spectrometer in the step 4 comprises sample stage movement, laser spot movement and movement of the sample stage and the laser spot; the shape of the laser spot in the scanning mode comprises a point spot, a line spot and a surface spot; the imaging process of the Raman spectrometer adopts a confocal Raman spectrometer 10 multiplied by a lens, the laser excitation wavelength is 785nm, and the laser power density is 4.6 multiplied by 10⁴W/cm²The acquisition time was 1 second.

Further, the information writing mode in step 1 includes handwriting, printing, coating and printing.

The invention also provides application of the steganographic material based on the surface enhanced Raman nanoparticles in the field of information security.

In the preferred embodiment of the invention, the steganographic ink is prepared by concentrating the synthesized 4-NBT-embedded surface enhanced Raman nanoparticles to 2.5nM, centrifuging 100 muL, removing the supernatant, adding 200 muL of hero brand pen ink diluted by 10 times, and ultrasonically mixing to obtain the 4-NBT steganographic ink. The surface enhanced Raman nanoparticles embedded with the 4-NBT are prepared by adding a 4-NBT ethanol solution into a gold core solution synthesized by a seed growth method as a base, then adsorbing, centrifugally washing and re-dispersing, and then growing a gold shell by a gold ion reduction method. The surface enhanced Raman nanoparticles in the steganographic ink have the characteristics of high safety and low cost due to simple manufacturing process and small material consumption.

In another preferred embodiment of the present invention, information is written using a mixture of multiple steganographic inks and common inks, and reading and extracting of the information is performed. The spectrum of the writing information of the steganographic ink is compared with the spectrum of the writing information of the common ink, so that the steganographic ink contains a characteristic peak of Raman molecules, is obviously distinguished from the common ink, can distinguish encrypted information from non-encrypted information, and has the characteristic of strong signal. Meanwhile, the Raman spectrum peak of each steganographic ink is narrow, and different Raman spectrum peak values can be selected to obtain the information combination multiplexing capability of the steganographic ink.

In another preferred embodiment of the present invention, the raman test is performed on the information written by the steganographic ink for a plurality of times, and the time nodes are respectively the current day, one week, two weeks, one month, two months and three months after writing, and are stored in the dark at ordinary times. Although the Raman signal of the steganographic ink is weakened along with the time, the Raman signal still keeps a considerable signal after three months, and the writing outline of the steganographic ink can be clearly identified, so that the steganographic ink prepared by the method has good long-term stability.

Therefore, the invention has the beneficial effects that: the invention provides a steganography material based on surface-enhanced Raman nanoparticles and a steganography method, which have the characteristics of safety, low cost, strong signal, good light stability and environment stability, and capability of realizing information combination multiplexing.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a bright field photograph of information written in steganographic ink with surface enhanced Raman nanoparticles embedded with 4-NBT Raman reporter molecules, taken from the Raman spectrum at 1310-1365cm^-1A Raman imaging graph drawn by the integral intensity of the Raman peak and Raman spectra of three points in the imaging graph;

FIG. 2 is a schematic of the structure of the surface enhanced Raman nanoparticle based on the present invention;

FIG. 3 is a brightfield photograph of information written by mixture of invisible ink and ordinary ink using surface enhanced Raman nanoparticles embedded with 1,4-BDT Raman reporter molecules, and 1030-1090cm in Raman spectrum^-1A Raman imaging graph drawn by the integral intensity of the Raman peak, an imaging graph processed by an algorithm and Raman spectra of five points in the imaging graph;

FIG. 4 is a brightfield photograph of information written in combination with steganographic ink of surface enhanced Raman nanoparticles embedded with 4-NBT Raman reporter molecules, steganographic ink of surface enhanced Raman nanoparticles embedded with 1,4-BDT Raman reporter molecules and normal ink, Raman imaging plots drawn by selecting different Raman peaks, and imaging plots of different combinations of information extracted after algorithm processing according to another preferred embodiment of the present invention;

FIG. 5 is a Raman imaging plot of a long-term stability test of information written in steganographic ink of surface-enhanced Raman nanoparticles embedded with 4-NBT Raman reporter molecules according to another preferred embodiment of the present invention, and 1310-1365cm of the Raman spectrum is selected^-1Integral intensity mapping of Raman peaksAnd then the product is obtained;

FIG. 6 is a Raman image of a sunshine stability test of information written in steganographic ink of surface enhanced Raman nanoparticles embedded with 4-NBT Raman reporter molecules according to another preferred embodiment of the present invention, and 1310-1365cm of Raman spectrum is selected^-1The integrated intensity of the raman peak is plotted.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.

The first embodiment is as follows: steganographic ink based on embedded 1,4-BDT Raman molecules

Step 1, preparing surface enhanced Raman nanoparticles (embedded with 1,4-BDT Raman molecule) with gold core-shell structure

Step 1.1, 2mL of gold core solution (particle diameter 25nm, dispersed in 100mmol/L cetyltrimethylammonium chloride solution (CTAC)) synthesized by 1nmol/L seed growth method is taken to be centrifuged and washed once, and the CTAC concentration is reduced to 20mmol/L and dispersed in the original volume.

Step 1.2, slowly adding 100 μ L of 1,4-BDT solution with the concentration generally larger than 2mmol/L, such as 3mmol/L, 4mmol/L, 5mmol/L and the like, standing for adsorbing for 2-4 hours, then centrifugally washing for multiple times (such as 2 times, 3 times, 4 times), and re-dispersing in 1mL of 50mmol/L CTAC to obtain gold core particles coated with 1,4-BDT molecules.

Step 1.3, combine 20mL of 50mmol/L CTAC and 1mL of a solution of 3-7mmol/L (e.g., 3.42mmol/L, 4.86mmol/L, 6.30mmol/L, etc.) chloroauric acid tetrahydrate.

Step 1.4, adding 600 μ L of 0.025-0.055mol/L (such as 0.03mol/L, 0.04mol/L, 0.05mol/L and the like) ascorbic acid solution and 1mL of the gold core solution coated with molecules synthesized in step 1.2 respectively, and rapidly oscillating in an ultrasonic pool to finally obtain the surface enhanced Raman nanoparticles embedded with 1,4-BDT molecules and having the core-shell structure. The structure of the granules is shown in figure 2.

And 2, preparing the steganographic ink.

And (2) concentrating the surface enhanced Raman nanoparticles embedded with the 1,4-BDT synthesized in the step (1) to 4nM, centrifuging 200 mu L, removing the supernatant, adding 100 mu L of hero brand pen ink diluted by 10 times, and ultrasonically mixing uniformly to obtain the 1,4-BDT ink.

Example two: steganographic ink based on embedded 4-NBT Raman molecule

Step 1, preparing surface enhanced Raman nanoparticles (embedded 4-NBT Raman molecule) with gold core-shell structure

Step 1.1, 2mL of gold core solution (particle diameter 25nm, dispersed in 100mmol/L cetyltrimethylammonium chloride solution (CTAC)) synthesized by a seed growth method with the concentration of 0.47nmol/L is taken for centrifugal washing once, and the CTAC concentration is reduced to 20mmol/L and dispersed in the original volume.

Step 1.2, slowly adding 100 mu L of 4-NBT solution into an ultrasonic pool, wherein the concentration of the solution is generally more than 8mmol/L, such as 9mmol/L, 10mmol/L, 11mmol/L and the like, standing for adsorption for 5-20 minutes, then centrifugally washing for multiple times, and re-dispersing in 1mL of 50mmol/L CTAC to obtain the gold core particles coated with 4-NBT.

Step 1.3, 16mL of 50mmol/L CTAC and 800. mu.L of a 3-7mmol/L (e.g., 3.42mmol/L, 4.86mmol/L, 6.30mmol/L, etc.) solution of chloroauric acid tetrahydrate are combined.

Step 1.4, respectively adding 480 mu L of 0.025-0.055mol/L (such as 0.03mol/L, 0.04mol/L, 0.05mol/L and the like) ascorbic acid solution and 960 mu L of the gold core solution coated with molecules synthesized in the step 1.2, and rapidly oscillating in an ultrasonic pool to finally obtain the surface enhanced Raman nanoparticles embedded with 4-NBT molecules and having the core-shell structure. The structure of the granules is shown in figure 2.

And 2, preparing the steganographic ink.

And (2) concentrating the surface enhanced Raman nanoparticles embedded with the 4-NBT synthesized in the step (1) to 2.5nM, centrifuging 100 muL, removing the supernatant, adding 200 muL of hero brand pen ink diluted by 10 times, and ultrasonically mixing uniformly to obtain the 4-NBT ink.

Example three: information is written and read using steganographic ink, as shown in FIG. 1.

Using the steganographic ink based on the embedded 4-NBT Raman molecule synthesized in example two, a pen was dipped into the appropriate amount to write a "dragon" on the paper, as shown in the upper left of FIG. 1.

Selecting 6.25X 6.5mm²Area, divided into 25 × 26 pixel points, and measuring the spectrum of the information by using a confocal Raman spectrometer 10 × lens, wherein the excitation wavelength is 785nm, and the laser power density is 4.6 × 10⁴W/cm²The acquisition time is 1 second, the Raman spectrum of each pixel is obtained, and 4-NBT 1310-^-1The integrated intensity of the raman peak is plotted on a raman image, as shown in the lower left of fig. 1. Raman imaging of visible written information is well matched with brightfield photographs. The three spectra on the right hand side of fig. 1 correspond to three points in raman imaging, respectively: 1 is the spectrum of paper, 2 and 3 are both the spectra of 4-NBT ink, and visible paper does not greatly interfere with information reading.

Example four: and writing information by using the mixture of the steganographic ink and the common ink, and reading and extracting the information. As shown in fig. 3.

Using the steganographic ink based on embedded 1,4-BDT Raman molecules synthesized in example one, a pen was dipped in an appropriate amount of 1,4-BDT ink to write "format" in "information" on paper, and the remaining letters were written with normal ink, as shown in the upper left of FIG. 3.

Selecting 24.4X 6.8mm²Area, divided into 61 × 17 pixel points, and measuring the spectrum of the information by using a confocal Raman spectrometer 10 × lens, wherein the excitation wavelength is 785nm, and the laser power density is 4.6 × 10⁴W/cm²The acquisition time is 1 second, the Raman spectrum of each pixel is obtained, and 1,4-BDT 1030-1090cm is selected^-1The integrated intensity of the raman peak is plotted on a raman image as shown in the left panel of fig. 3. As shown, only information written with steganographic ink containing surface enhanced Raman nanoparticles can be Raman printedAnd the information is displayed in the imaging process, and the information is different from that in the bright field. Hiding of the actual information can be performed with steganographic ink.

The 5 tensioman spectra on the right side of fig. 3 correspond to the 5 points in the top left and middle left of fig. 3, respectively: 1 is the spectrum of paper, 2 and 4 are the spectra of ordinary ink, and 3 and 5 are the spectra of the weaker and stronger signals of 1,4-BDT ink, respectively. Comparing the spectrum No. 5 with the spectrum No. 2 and 4 shows that the 1,4-BDT ink contains characteristic peaks of Raman molecules and is obviously different from common ink.

Due to uneven paper, the background of some places is higher, so that false positive signals (such as false positive signals) appear in a Raman imaging image

Point 4 in fig. 3), so the signals are removed using Classical Least Squares (CLS).

The spectra of paper, plain ink, 1,4-BDT ink and higher background signal are taken as reference components and the algorithm obtains the best fit spectra by optimizing the coefficients of the different components. The signals of the three components of paper, regular ink and higher background are indicated in dark color and the signals of the 1,4-BDT ink are indicated in light color. The color of each pixel in the imaged picture is determined by the color of the component with the highest index. The resulting image after processing is shown in the bottom left of FIG. 3, where it can be observed that the false positive signal has been removed, leaving only the signal of the 1,4-BDT ink.

Example five: and (3) writing information by mixing different steganographic ink and common ink, and reading and extracting the information. As shown in fig. 4.

The paper was written with "aei" of "abcdefghi" by dipping with a pen an appropriate amount of the 4-NBT ink obtained in example two, and "bdfh" of "abcdefghi" by dipping an appropriate amount of the 1,4-BDT ink obtained in example one, and the letter "cg" was written with a normal ink, as shown in 1-1 of FIG. 4.

Selecting 11.1X 12.3mm²Area, divided into 37 × 41 pixel points, and spectrum of the information is tested by using a confocal Raman spectrometer 10 × lens, with excitation wavelength of 785nm and laser power density of 4.6 × 10⁴W/cm²And the acquisition time is 1 second, and the Raman spectrum of each pixel is obtained.

In order to obtain different combinations of information, different raman peaks are used for imaging.

Selecting 1310-^-1Integrated intensity of raman peak was plotted on a raman graph representing information of 4-NBT ink, see 2-1 of fig. 4;

as the 1,4-BDT ink and the 4-NBT ink are at 1090cm from 1030-^-1There is a peak overlap, so only 1030-^-1Integral intensity of Raman peaks Raman imaging is performed to represent the information of the 1,4-BDT ink, which is shown as 2-2 in FIG. 4, and the information profile is not obvious;

selecting 1110 + 1165cm^-1Drawing a Raman imaging graph by the integral intensity of the Raman peak, representing the information of the common ink, as shown in 2-3 of FIG. 4, because the surface enhanced Raman nanoparticles embedded with the 1,4-BDT molecules simultaneously enhance the signals of the ink molecules, the information written by the 1,4-BDT ink is shown;

select 1030 and 1090cm^-1Integral intensities of raman peaks were plotted for raman imaging representing information on the mixing of 1,4-BDT ink and 4-NBT ink, see 2-4 of fig. 4;

selecting 1310-^-1Drawing a Raman imaging graph by the integral intensity of the Raman peak, adjusting a threshold value, representing the information of the mixture of the common ink and the 4-NBT ink, as shown in 2-5 of FIG. 4, and obtaining the information of the mixture of the 1,4-BDT ink and the 4-NBT ink actually due to the enhancement of the ink molecules by the surface enhanced Raman nanoparticles embedded with the 1,4-BDT molecules;

1540-channel 1600cm selection^-1The integrated intensities of the raman peaks plot a raman image representing information for a mixture of three inks, see 2-6 in fig. 4, with virtually no information for a common ink.

Based on the limitations of imaging with a single raman peak in the above results, Classical Least Squares (CLS) based on spectral shape is used to separate and extract information. The spectra of paper, common ink, 4-NBT ink and 1,4-BDT ink are used as reference components, and the optimal fitting spectrum is obtained by optimizing coefficients of different components through an algorithm. The reference spectrum is set to light and the rest to dark, the color of each pixel in the image is determined by the color of the component with the highest coefficient.

In FIG. 4, 3-1 is the writing information of 4-NBT ink, 3-2 is the writing information of 1,4-BDT ink, 3-3 is the writing information of normal ink, 3-4 is the combined writing information of 4-NBT ink and 1,4-BDT ink, 3-5 is the combined writing information of 4-NBT ink and normal ink, 3-5 is the combined writing information of 1,4-BDT ink and normal ink, and 3-7 is the three-ink combined writing information. Therefore, information hiding and combining can be achieved based on the surface enhanced Raman nanoparticle steganography ink combination algorithm.

Example six: long-term stability testing of steganographic inks. As shown in fig. 5.

And performing Raman tests on the dragon written in the third embodiment for multiple times, wherein time nodes are 1-1, 1-2 a week, 1-3 a week, 1-4 a month, 1-5 a month and 1-6 a month respectively after the dragon is written, and the test parameters are the same as those of the third embodiment and are stored in the dark at ordinary times. Selecting 4-NBT 1310-^-1The integrated intensity of the raman peak is plotted in a corresponding raman image, see figure 5. As shown in the figure, the Raman signal of the steganographic ink is weakened along with the time, but a considerable signal is still kept after three months, so that the outline of the dragon can be clearly identified, and the steganographic ink prepared by the method has good long-term stability.

Example seven: and (4) testing the sunshine stability of the steganographic ink. As shown in fig. 6.

Using a pen, a suitable amount of the 4-NBT ink prepared in example two was dipped and written "sun" on paper, and 7.8X 4mm was selected²Area, divided into 39 × 20 pixel points, and spectrum of the information is tested by using a confocal Raman spectrometer 10 × lens, with excitation wavelength of 785nm and laser power density of 4.6 × 10⁴W/cm²The acquisition time is 1 second, the Raman spectrum of each pixel is obtained, and 4-NBT 1310-^-1The integrated intensity of the raman peak is plotted on a raman image as shown in fig. 61-1.

It was then placed under sunlight for 6 hours from 10 am to 4 pm for two consecutive days and raman imaged with the same parameters as above each day. The image after the first sun exposure is shown in FIG. 61-2, and the image after the second sun exposure is shown in FIG. 61-3. As can be seen from the figure, the signal of the steganographic ink has no obvious change under the sun irradiation for two consecutive days, which shows that the sunshine stability is better.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A steganography method, comprising the steps of:

step 1, a party A records information by using one or more steganographic materials based on surface enhanced Raman nanoparticles and common materials respectively and encrypts the information;

step 3, the party A transmits the record information to the party B;

step 4, the second party utilizes a Raman spectrometer to scan or image and read the Raman spectrum information of one or more steganographic materials based on the surface enhanced Raman nanoparticles and the common materials;

step 5, the second party obtains the optimal fitting spectrum by optimizing coefficients of different components by using a classical least square method on the obtained Raman spectrum information;

step 6, the party B combines the optimal fitting spectrum according to the encryption mode and the combination mode, and decrypts the optimal fitting spectrum to obtain hidden information;

the steganographic material is also characterized in that surface enhanced Raman nanoparticles are added into the steganographic material; wherein the surface-enhanced Raman nanoparticles are composed of a metal nano-substrate and a characteristic Raman molecule; the structure of the metal nanometer substrate comprises a nanometer core-shell particle structure, nanometer flowers, nanometer triangular plates, nanometer spheres, nanometer rods, nanometer stars, nanometer dendrites or nanometer particle dimers, the characteristic Raman molecule comprises p-dimercaptobenzene (1,4-BDT), 4-nitrothiophenol (4-NBT), o-nitrothiophenol (2-NBT), 2-mercapto-5-nitrobenzimidazole (2-M-5-NBI), 2-mercapto-6-nitrobenzothiazole (2-M-6-NBT), biphenyl-4, 4 '-dithiol (4,4' -BPDT), 4-toluenethiol (4-MBT), o-chlorothiophenol (2-CBT), 4-chlorothiophenol (4-CBT) or 2-naphthalene thiol (2-NT); the steganographic material comprises steganographic ink, steganographic toner, steganographic pigment or steganographic paint; the nano core-shell particle structure comprises three layers, wherein the inner layer and the outer layer are both the metal nano substrate, and the middle layer is the characteristic Raman molecule.

2. The steganographic process of claim 1 wherein said common material in said step 1 and said step 4 comprises common ink, common toner, common pigment or common paint.

3. The steganography method according to claim 1, wherein the scanning mode of the imaging process by the Raman spectrometer in the step 4 comprises sample stage movement, laser spot movement and both movement; the shape of the laser spot in the scanning mode comprises a point spot, a line spot and a surface spot; the imaging process of the Raman spectrometer adopts a confocal Raman spectrometer 10 multiplied by a lens, the laser excitation wavelength is 785nm, and the laser power density is 4.6 multiplied by 10⁴W/cm²The acquisition time was 1 second.

4. The steganographic method according to claim 1 wherein said means of recording information in step 1 includes handwriting, printing, painting and printing.

5. Use of the steganographic method according to claim 1 in the field of information security.